Introduction: Cystic fibrosis (CF) is the most common genetic autosomal recessive genetic disease. The most serious symptoms are observed in the lungs. Recurrent respiratory infections are the main cause of hospitalization and death among cystic fibrosis patients. Pathogens that commonly infect the airways of adult CF patients include Staphylococcus aureus and Pseudomonas aeruginosa. The aim of this study was to analyse the microorganisms cultured from the airways of adult CF patients and to perform antimicrobial resistance tests of the most frequently isolated bacteria. Material and methods: In this study, 1422 isolates of 89 CF patients were collected during a 4-year period. The microorganisms were cultured and identified according to standard microbiological procedures. Identification and drug susceptibility were performed in a Phoenix (BD) automatic system, Vitek2Compact (bioMérieux) and disk-diffusion method by Kirby-Bauer. Among the 1422 strains, the most frequent pathogens were Pseudomonas aeruginosa (55.6%) and Staphylococcus aureus (37.8%). A total of 482 (61%) strains of 790 isolates of P. aeruginosa were identified as P. aeruginosa of mucoid phenotype. The isolates with mucoid phenotypes were more susceptible than non-mucoid. Eighty-six strains of S. aureus showed resistance to methicillin (MRSA), which accounted for 16.0% of all strains of S. aureus. Conclusions: The analysis of microbiological materials from adult CF patients treated in IGiChP allowed us to determine the prevalence of potentially pathogenic microorganisms. The data obtained are consistent with literature.